Elster GmbH
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EnCal 3000 Quad– Hardware Manual
22/06/2017
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2.9.1
Double Block and Bleed Function
After small particles are filtered out by the inlet filters in the inlet couplings, the pressure is reduced to
approximately 0.8 barg. From the pressure regulators the gas will flow to the manifold. There are several
valves mounted on the manifold.
The two most right valves are purge valves. The upper purge valve is the sample bypass valve (Activated by
timed relay 2). The lower is a helium purge valve and activated by timed relay 3.
The stream and calibration valves form pairs that are actuated at the same time.
The valves left from the purge valves are used for the calibration. Next to the calibration valves there are 1
up to 5 pairs used for the streams. Depending on the configuration the manifold can support up to 3 or up to
6 streams (including the calibration gas stream). Unused positions on the manifold are blocked.
Gas will enter at the first (lower) valve which will guide the flow to the second (upper) valve in actuated
situation. The second valve guides the flow into a common channel. In deactivated situation, the input from
the first valve is blocked and the output is linked to the relieve port of this valve, which vents to the SBV vent.
The input of the second valve is also blocked so it is not possible to build up pressure between both valves.
In case one or both valves would leak, the pressure between the valves won’t rise above the pressure that is
present in the common channel because of the vent to the SBV vent, so mixing up the streams is not
possible.
2.9.2
Internal Sample Bypass
The output from all second valves is combined on the common channel. Depending on which channel is
activated, a section of this channel and the deactivated valves, form a dead volume. The outputs from
deactivated valves are therefore relieved to a second common vent channel, which is blocked by the sample
bypass valve. Activating this valve will result in a flow from the activated valves, through the deactivated
valves, to the bypass valve. This refreshes all second valves and the common channels with the new gas, so
all dead volumes are refreshed. Actuating the bypass valve results in a flow that is approximately 15 times
higher than the normal flow. The purge valve should be activated for a short period (±30 seconds default)
when a new stream is selected.
The new stream is selected one analysis prior to the injection, so during the analysis the new sample is
already flushed through the manifold. The best moment to activate the sample purge is ending 10 seconds
before the injection and then extended to the front depending on the purge duration. For long sample lines or
higher sample line pressures the purge time may be extended to where the new stream was selected. Keep
in mind the purge time also applies to the calibration gas which must be purged, but larger purge times and
frequent purging will deplete the bottle faster. Further information for the needed setting in the software can
be found in the software manual.
The flow through the analytical modules will be reduced during the activation of the bypass, but will continue.
Closing the bypass valve will restore the normal flow to the analytical modules. After the sample gas has
passed the manifold it becomes split for the transport to the two analytical channels that are installed in the
master unit. The vent outputs from both modules are returning to the manifold and are combined to two
venting outputs. The sample output from the manifold in the Master Unit is connected with the inlet for the
sample gas connection from the Slave Unit. In the Slave Unit the sample gas flow is also split for the
transport to the two analytical channels that are in the slave unit. The sample gas flow can be also increased
for the Slave Unit with an additional Purge Valve. The output gases from these channels are combined again
and become transported to the SBV connection of the Slave Unit.
